T-bars vs Stored energy

Ok, with that set-up you have there, the spring rate is going to be off the chart stiff. That leverage point at the rear shackle is an important tuning element. Longer the point, softer the spring, shorter=stiffer. You've got that car sitting on construction girders. Going back to the pinion snubber...it could never work properly with springs that taught. I would just toss a pair of normal shackles on that, and then try your snubber again. I'm sure that'll do the trick.